1. Technical Field
The present invention relates to a liquid crystal display device that is driven in accordance with a field sequential drive scheme, and more specifically to a liquid crystal display device for which the high speed sequential drive scheme can be employed.
2. Prior Art
A field sequential drive scheme has been employed to display a color image on a liquid crystal display (LCD) device without using a color filter. According to the field sequential drive scheme, image data for one color are written to an LCD panel, and when a response time required for switching the state of liquid crystal molecules has elapsed, a backlight for that color is turned in to display the image data. This repetitious operation is performed for red (R), green (G) and blue (B) colors. In order to provide a satisfactorily extended turn-On period for a backlight, a high speed writing circuit (high speed driver) and a high speed liquid crystal material are required. When the LCD panel is driven at a frame frequency Ff (Hz), the time available for displaying an image in one color is ⅓ Ff, and during this time, the writing of the image data to the LCD panel, the switching of the state of the liquid crystal material and the display of an image using the backlight must be completed. When, for example, the response time of the liquid crystal material is 3 ms, Ff=60 Hz and the duty ratio of the backlight is 10%, the period Twrite(s) for writing data to the LCD panel is represented by the following equation:
Twrite={fraction (1/180)}xe2x88x92{fraction (3/1000)}xe2x88x920.1xc3x97{fraction (1/60)} (s)xe2x89xa0889xe2x80x83xe2x80x83(xcexcs).
When an LCD panel using an XGA scheme (1024 picture elements (pels) (horizontally) xc3x97768 pels (vertically) is employed, the time for writing one horizontal pel line is approximately 1 xcexcs.
Such a high speed writing operation for one pel line can not be achieved by a currently available thin film transistor (TFT) that is made of an amorphous semiconductor and that has an operational speed of approximately 20 xcexcs. To provide such a high speed writing operation requires the employment of a TFT made of polysilicon, a high speed liquid crystal material, and a high speed driver having an operational speed that is higher then that of currently available drivers. However, a TFT made of polysilicon, a high speed liquid crystal material, and a high speed driver would be very expensive.
It is, therefore, one subject of the present invention to provide a low cost LCD device for which a high speed field sequential drive scheme can be employed that uses a currently available low cost write driver, and a low cost liquid crystal material.
The present invention is thus directed to a liquid crystal display device comprising: a liquid crystal display array divided into a first area, a second area and a third area, in each of which are included a plurality of pel lines; a first means for performing an operation for sequentially writing first color data, selected from data provided for red, green and blue, along the plurality of pel lines in the first area, an operation for sequentially writing second color data, selected from the data provided for red, green and blue, along the plurality of pel lines in the second area, and an operation for sequentially writing third color data, selected from the data provided for red, green and blue, along the plurality of pel lines in the third area; a backlight means, which is divided into N backlight sections (N is a multiple of 3 and is equal to or greater than 6) and which selectively generates red light, green light or blue light, wherewith N/3 backlight sections illuminate the first area, N/3 backlight sections illuminate the second area and N/3 backlight sections illuminate the third area; and a second means for sequentially activating the N/3 backlight sections for the first area to generate first color light and sequentially displaying the first color data in the first area, for sequentially activating the N/3 backlight sections for the second area to generate second color light and sequentially displaying the second color data in the second area, and for sequentially activating the N/3 backlight sections for the third area to generate third color light and sequentially displaying the third color data in the third area.
The first means performs simultaneously the operation for writing the first color data, the operation for writing second color data and the operation for writing the third color data.
The first area, the second area and the third area are each divided into N/3 sub-areas, and in each of the sub-areas are included a plurality of pel lines.
When one color data set is written in one of the sub-areas, the second means activates a backlight section assigned for the sub-area, and before another color data set is written in the sub-area, the second means deactivates the backlight section.
The same number of pel lines are included in the first area, the second area and the third area.
When one part of one color data set is displayed in one of the sub-areas, the following part of the color data is written in the succeeding sub-area.
When one part of one color data set is displayed in one of the sub-areas, the following part of the color data is written across the pel lines in the succeeding multiple sub-areas.
A backlight section assigned for one of the sub-areas is turned on following the expiration of a response time for a liquid crystal material in the last pel line in the sub-area.
The first means writes the first color data, the second color data and the third color data at predetermined intervals in one of the sub-areas, and a backlight section assigned for the sub-area generates light for the first color when the first color data have been written, generates light for the second color when the second color data have been written, and generates light for the third color when the third color have been written.
The second means controls the N backlight sections so as to sequentially display the color data written in the sub-areas during a period 1/Ff (Ff is a frame frequency).
According to another aspect of the present invention, a liquid crystal display device comprises: a liquid crystal display array, which includes horizontally arranged X pels and vertically arranged Y pels, which is divided into a first area, a second area and a third area, in each of which are included horizontally extended Y pel lines, and which is divided into N/3 sub-areas (N is a multiple of 3 and is equal to or greater than 6); a first means for performing an operation for sequentially writing first color data, selected from data provided for red, green and blue, across Y pel lines beginning with the first pel line in the first area, continuing through the pel lines in the second area and ending with the last pel line in the third area, for performing an operation for sequentially writing second color data, selected from the data provided for red, green and blue, across Y pel lines beginning with the first pel line in the second area, continuing through the pel lines in the third area and ending with the last pel line in the first area, and for performing an operation for sequentially writing third color data selected form the red, green ad blue data into Y pel lines beginning with the first pel line in the third area, continuing through the pel lines in the first area and ending with the last pel line in the second area; a backlight means, which is divided into N backlight sections and which selectively generates red light, green light or blue light, wherewith N/3 backlight sections illuminate the first area, N/3 backlight sections illuminate the second area and N/3 backlight sections illuminate the third area; and a second means for controlling the N backlight sections, so that when one color data set, selected from the data provided for red, green and blue, have been written to one of the sub-areas, a backlight section assigned for the sub-area is turned on to generate a light having the same color as the color data set.
According to an additional aspect of the present invention, a liquid crystal display device comprises: a liquid crystal display array in which are included a plurality of pel lines; a first means for sequentially writing across the plurality of pel lines first color data selected form data provided for red, green and blue, for sequentially writing across the plurality of pel lines second color data selected from the data provided for red, green and blue, and for sequentially writing to the plurality of pel lines third color data selected from the data provided for red, green and blue; a backlight means, which is divided into N backlight sections (N is an integer equal to or greater than 2) and which selectively generates red light, green light or blue light, whereof each of the N backlight sections is assigned for a 1/N area in the liquid crystal display array; and a second means for sequentially activating the N backlight sections in order to sequentially display the color data written across the plurality of pel lines in the liquid crystal display array.
When one color data set has been written across pel lines in the 1/N area, the second means activates a backlight section assigned for the 1/N area to generate a light having the same color as the color data set, and then, before another color data set is written to the 1/N area, the second means deactivates the backlight section.
According to a further aspect of the present invention, a liquid crystal display device comprises: a liquid crystal display array, each of which includes a plurality of pel lines that are sorted into a plurality of pel line groups, each of which includes at least two continuous pel lines; a first means for sequentially writing to the plurality of pel line groups first color data selected from data provided for red, green and blue, for sequentially writing to the plurality of pel line groups second color data selected from the data provided for red, green and blue, and for sequentially writing to the plurality of pel line groups third color data selected from the data provided for red, green and blue; a backlight means, which is divided into N backlight sections (N is an integer equal to or greater than 2) and which selectively generates red light, green light or blue light, whereof each of the N backlight sections is assigned for a 1/N are in the liquid crystal display array; and a second means for sequentially activating the N backlight sections in order to sequentially display the color data written across the plurality of pel line groups in the liquid crystal display array.